This invention relates to an improvement in a method of impregnating carbon electrodes with pitch and more particularly to a method of continuously impregnating carbon electrodes with pitch, which enables working circumstances to be maintained in good condition, reduces the danger of fire and keeps transporting means in good condition.
In general, carbon electrodes are produced by a method comprising adding pitch to aggregates including carbon such as coke, etc. as a main part thereof, kneading said mixture, then subjecting said kneaded mixture to press or extrusion working to make formed blocks, burning and sintering the resultant formed blocks at a temperature of 1500.degree. C. or so, and thereafter burning the sintered blocks at a temperature between 2,500.degree. and 3,000.degree. C. thereby causing graphitization thereof. In a series of these steps, in order to obtain electrodes of higher density and strength, the formed and sintered blanks for electrodes are impregnated with pitch to fill up fine cavities existing in the interior thereof.
Heretofore, as a method of carrying out such impregnating treatment of carbon electrodes with pitch, there has been known a method comprising piling up carbon electrodes on a palette, heating and drying said electrodes on the palette in a drying furnace, thereafter placing them in an impregnation tank to impregnate them with pitch, and after the completion of impregnation, cooling them in a cooling tank. Namely, once the carbon electrodes have once been piled up on a palette, the palette and carbon electrodes are moved as a single body through the series of heating, drying, pitch impregnating and cooling steps, with the result that the palette is also subjected to the same treatment as the carbon electrodes.
As a result, in the prior art treatment, there are difficulties in that in the impregnation step the palette is inevitably coated with pitch and is heated at a high temperature in the drying furnace resulting in melting of the pitch and production of pitch gas, which contaminates the working environment and fires. Additionally, the molten pitch adheres to the transporting device for the palette in the drying furnace and to various parts of said transporting device and causes aggravation of the movement thereof as well as its failure. Also, the pitch attached to the palette is exposed repeatedly to high temperatures, so that it is carbonized and grows in lameller structure, resulting in periodic cleaning of the palette being required. This cleaning operation is fairly troublesome and requires many hands and much time and causes an increase in and interruption of the production steps.